Implantable medical devices (IMDs) such as pacemakers and implantable cardioverter defibrillators are utilized in monitoring and regulating various conditions within the body. An implantable cardioverter defibrillator, for example, is often utilized in cardiac rhythm management applications to monitor the rate and rhythm of the heart and for delivering various therapies such as cardiac pacing, cardiac defibrillation, and/or cardiac therapy. In some systems, the implantable cardiac defibrillator can be configured to sense various physiological parameters occurring in the atria and/or ventricles of the body to determine the occurrence of any abnormalities in the operation of the patient's heart. Based on these sensed parameters, an appropriate therapy may then be delivered to the patient.
Present techniques used for detecting events occurring within the heart are sometimes ineffective at discriminating between subtle differences in electrical heart activity, which can affect the type of treatment provided to the patient. In the detection of an event such as ventricular tachycardia (VT), for example, many present techniques are unable to accurately differentiate the event from another event such as a wide-complex supraventricular tachycardia (SVT), which often appears similar to ventricular tachycardia on an electrocardiogram (ECG) or electrogram (EGM). In contrast to ventricular tachycardia, the occurrence of supraventricular tachycardia may not be problematic, and may entail a different, less drastic form of therapy. Ventricular tachycardia, on the other hand, is a potentially lethal condition, and requires immediate medical therapy often in the form of shock therapy.
To discriminate between these events, many IMDs utilize interval-based and/or morphology-based algorithms, which rely on the analysis of electrical signals from an ECG or EGM. In some cases, the presence of electrical noise or interference within the body due to the pacing artifact (e.g., noise generated by a pacemaker) or from other sources may affect the ability of the sensor leads to accurately detect signals. While such techniques are effective in detecting certain types of events, they are sometimes ineffectual in discriminating between events such as ventricular tachycardia and supraventricular tachycardia.